1. Technical Field
One or more embodiments of the present invention relate to a motor control apparatus that controls a motor by a Pulse Width Modulation (PWM) method.
2. Related Art
For example, in an electric power steering apparatus of a vehicle, in order to give to a steering mechanism a steering assist force depending on a steering torque of a steering wheel, an electric motor such as a three-phase brushless motor is provided. As an apparatus for controlling rotation of the motor, a motor control apparatus using a PWM method is known.
Generally, the motor control apparatus of the PWM method includes a PWM signal generation unit that generates and outputs a PWM signal, an inverter circuit that drives the motor based on the ON/OFF states of a switching element in response to the PWM signal, a current detection unit that detects a current (a motor current) flowing in the motor, and a control unit that performs feedback control with respect to the PWM signal generation unit so as to output the PWM signal having a predetermined duty, based on a deviation between a detected value of the motor current and a target value. The motor control apparatus of such a PWM method is disclosed in JP-A-2011-152027, JP-A-2010-226899, JP-A-2012-120296, and JP-A-2013-113695.
In JP-A-2011-152027, a drive apparatus of two systems for driving a motor having two windings is provided and includes an inverter circuit in each system. Then, a PWM signal that is generated in one PWM signal generation unit is output by branching to two inverter circuits.
In JP-A-2010-226899, a drive apparatus of two systems for driving a motor having two windings is provided and includes an inverter circuit and a PWM signal generation unit in each system. Then, a PWM signal generated in each PWM signal generation unit is output to a corresponding inverter circuit.
In JP-A-2012-120296, two inverter circuits for driving two motors, respectively and one control unit for controlling the inverter circuits are provided. Furthermore, the control unit includes two PWM signal generation units. Then, a PWM signal generated in each PWM signal generation unit is output to a corresponding inverter circuit.
In JP-A-2013-113695, two inverter circuits for driving one motor and two control units for controlling the inverter circuits respectively are provided. Output sides of respective inverter circuits are coupled to each other and are connected to the motor. Then, a PWM signal generated in each of the two control units is output to a corresponding inverter circuit.